Exploring the Natural History of Native Seabird Predators

While they spend the majority of their lives on the open ocean, large populations of seabirds return to near-shore coastal islands to breed on an annual basis. During these periods, seabirds share territory with native terrestrial carnivores who live and forage in the coastal environment. Predation is an inevitable result of this overlap, but the effect of native carnivores on nesting seabird populations remains largely understudied. Effectively quantifying the impacts of predation on seabird population dynamics requires consistent long-term demographic datasets; the collection of these data is expensive, logistically challenging, and can cause major disruption to breeding seabirds.

As an alternative to intensive population monitoring, we can closely study the behavior of native predators active at seabird islands to gain a qualitative understanding of the conservation threat which they pose. Various aspects of predator foraging, social, and movement ecology can exacerbate or buffer their impacts to vulnerable seabird populations. By using an observation-based natural history approach, we can identify the most problematic predators and inform species-specific management interventions.

A solar powered cell-phone linked camera trap. 

Luke Stuntz searching for river otter scat. 

Fish bones from a river otter scat for identification. 

Managing Seabird Predators in Southern Oregon

Roughly 450,000 breeding Leach’s storm-petrels nest on just seven small islands and rocks along a twenty-mile stretch of coastline in southern Curry County, Oregon. Leach’s storm-petrel populations are declining globally, and a near-complete colony collapse has been observed at one of the major nesting sites in Oregon. All of the storm-petrel colony islands in Oregon are less than a half kilometer from shore, rendering them vulnerable to the impacts of native terrestrial carnivores. As the United States Fish & Wildlife Service moves towards more proactive management of these sites, we are hoping to understand how large of a threat native carnivores pose and whether predator control might be an appropriate conservation intervention.

Beginning in 2023, we have been using a suite of different field methods to understand the presence and activity of native carnivores at these islands, with a focus on two mustelid species: northern river otter and American mink. Solar-powered cellular camera trap arrays provide us with a 24/7 feed of mammalian activity on the islands, while the analysis of prey remains in carnivore scat provides data on the relative contribution of different taxa to predator diets. These methods are complemented by regular observational surveys on the seabird islands, during which we document tracks, scat, dens, and prey remains to provide a holistic understanding of predator activity. These monitoring efforts provide site-specific insights into real time impacts to seabird populations, allowing our project partners to quickly implement appropriate management actions. We will be working closely with USFWS to develop a framework for a long-term, sustainable, and financially realistic predator management program that can alleviate one of the major stressors influencing seabird nesting success in southern Oregon. You can read more about our field work in summer 2023 on our blog!